Multiple switch control assembly with multiple pushbutton interlock latch bar and safety switch

ABSTRACT

A multiple push button assembly with abutment members on each pushbutton are securely held in undercut portions of a single latch bar in the respective pushbutton switch operative positions. More than one pushbutton assembly may be simultaneously actuated and interlocked in the operative position.

United States Patent 1 Constable June 12, 1973 MULTIPLE SWITCH CONTROLASSEMBLY WITH MULTIPLE PUSHBUTTON' INTERLOCK LATCH BAR AND SAFETY SWITCH[75] Inventor: Philip James Constable, Uxbridge,

England [73] Assignee: Drayton Controls Limited, West Drayton,Middlesex, England 22 Filed: Dec. 15, 1971 211 App]. No.: 208,208

[30] Foreign Application Priority Data Dec. 22. 1970 Great Britain..60826/70 [52] US. Cl 200/5 R, 200/5 B [51] Int. Cl. H0111 9/26 [58]Field of Search 200/5 EB, 5

{56] References Cited UNITED STATES PATENTS 2,934,925 5/1960 Henshaw,Jr. et a]. 200/5 EB X 1/1967 Woodward 200/5 EB 4/1960 Stoner et al.200/5 EB Primary ExaminerJ. R. Scott AttorneyJoseph F. Brisebois et a1.

57 ABSTRACT A multiple push button assembly with abutment members oneach pushbutton are securely held in undercut portions of a single latchbar in the respective pushbutton switch operative positions. More thanone pushbutton assembly may be simultaneously actuated and interlockedin the operative position.

8 Claims, 8 Drawing Figures lil j PATENTED JUN I 2 I973 same or 3 FIG 6FIGS.

PATENIED 3.739.110

SHEET'S 0f 3 LOAD LOAD

Y LUAD UFF QN 10 62215 5 LOAD 0N QN LOAD F194. F/c].

This invention relates to an electrical switch device for controlling acentral heating system.

It is becoming increasingly important in domestic heating control toprovide a programming switch which is capable of selecting complexcombinations of hot water and central heating functions. Thus,sophisticated switching is envisaged whereby, for example, time periodsfor the two functions and predetermined levels of control for thecentral heating can be selected. If such control is to be achieved,switches will have to be incorporated in the programmer which can supplycurrent to perhaps two circulating pumps at say 0.7 amperes each(inductive), and in the case of a large domestic oil-fired boiler to afan/oil pump motor at say 3 amperes (inductive). In addition, lowcurrents will have to be applied to control circuits to achieve thecurrent conditions of heating and, as said previously, the motors andcircuits will have to be supplied in many variations and combinations.Such complex selection inevitably requires a number of switches, thecurrent carrying capacity of which would have to be in the order of 5amperes. Unfortunately, however, as explained below, the problem doesnot end here because the current switching capacity of the switches willalso have to be of the order of 5 amperes. Furthermore, there are twocritical positions in which a switch is liable to be damaged. Firstly,when connection is made, the in rush" current may be many times largerthan the final steady current. Secondly, when connection is broken, adestructive arc can be drawn between the contacts if the load isinductive. The latter is generally the more troublesome. In fact,current switching capacity is always less than the current carryingcapacity and if the current cannot be guaranteed to be less than theswitching capacity of the switch at the instant of switching, then thecarrying capacity must, in order to prevent damage, be restricted tothat of the switching capacity. Switches used for central heatingcontrol must meet this requirement since switching of relatively highcurrent inductive loads is necessary.

Although complex selection can be achieved using a number of relativelyheavy duty switches each of which has a current carrying and switchingcapacity of the order of 5 amps, clearly such an arrangement would bespace consuming and uneconomic. As a compromise, therefore, it has beencommon practice to have less sophisticated selection using these higherrated switches. An alternative to this is to carry out the programswitching at low currents and use these to switch the heavier currentswith relays. This too is unwieldy and expensive.

According to the present invention there is provided an electricalswitch device including a number of selector switches and a safetyswitch which are connectible, in use, in a current supply circuit for aload to be controlled by the device; and mechanical means which, in use,actuate the safety switch to isolate a given selector switch from thecurrent supply circuit while it is in the process of switching and toconnect it in the circuit when switching is completed; the safety switchhaving a current switching capacity higher than that of the selectorswitch so that during switching of the latter contact, arcing isprevented.

Preferably, the safety switch isolates all the selector switches fromthe current supply circuit whilst a given selector switch is in theprocess of switching. Then, whilst program switching is carried out bythe selector switches the safety switch switches off the supply.Consequently, each selector switch can have a relatively low switchingcapacity, for example, 0.2 amperes, it only being necessary to providethe safety switch with a high switching capacity of, for example, theorder of 5 amperes.

The mechanical means may be such that if one or more selector switchesare in the"on position, it or they can be returned to the off" positionby moving another selector switch from the off" to the on" position.

The mechanical means may include a longitudinally movable latch bar.Each selector switch may be in the form of a spring-loaded push buttonhaving a longitudinally movable lever adapted to engage the latch bar tocause longitudinal movement thereof. The latch bar may be provided witha number of cam surfaces and each lever may be provided with an abutmentmember, each member being adapted to engage a corresponding one of thesurfaces tocause longitudinal movement of the latch bar. Each camsurface may be provided with an undercut portion so that after apredetermined movement of the latch bar in one direction, the abutmentmember disengages the cam surface and latches in the undercut portion.The latch bar may be spring biased in a direction opposite to the onedirection, so that when the abutment member leaves the cam surface, thelatch bar is moved in the opposite direction and the abutment memberlatches in the undercut portion. The safety switch may be of thesnap-action type and is provided with a spring biased plunger againstwhich one end of the latch bar engages. Each lever may support one ormore electrical contacts which are adapted to engage or disengage one ormore stationary electrical contacts during movement of the lever.Movement of each lever may be at right angles to the movement of thelatch bar.

The invention will now be described in more detail, by way of example,with reference to the accompanying drawings in which:

FIG. 1 is a diagrammatic plan view of a push button switch assembly fora central heating system;

FIG. 2 is a view as seen in the direction of arrow X in FIG. 1;

FIG. 3 shows in more detail an individual push button assembly and itsassociated actuating lever;

FIGS. 4 (a), (b), (c), (d) and (e) all show a detail of a latch bar ofthe switch assembly shown in FIG. 1, and each illustrate a particularoperational position thereof;

FIG. 5 shows in detail a plan view of a movable contact carrier of theassembly shown in FIG. 1;

FIG. 6 shows an end elevation of the carrier shown in FIG. 4 in anoperative position relative to a stator terminal member of the assemblyshown in FIG. 1;

FIGS. 7 (a), (b), (c), (d) and (2) all diagrammatically illustrate howthe switch assembly of FIG. 1 is connected in circuit, and each show aparticular operational condition; and

FIG. 8 is a diagrammatic illustration of a microswitch.

Referring to the drawings, FIG. 1 shows a push button switch assemblyincluding a base plate member 1 on which is mounted a bank of eightselector or push button switches indicated generally at 2. Each of theselector switches 2 is spring-loaded and when depressed causes movementof a latch bar 3 to the right as shown in FIG. 1 to actuate a safetyswitch in the form of a snap-action microswitch 4.

The microswitch illustrated diagrammatically in FIG. 8 is ofconventional form and is such that depression of the plunger 5 causes amovable contact C to move with a snap-action out of contact with a firstterminal T into contact with a second terminal T and then, when theplunger is released back into contact with the first terminal T Thismovement of the contact is provided by a simple lever mechanism L L andspring, S, mounted on a fixed bracket B.

It will be understood, of course, that switch constructions differentfrom that just described can be used provided the switch has a highercurrent switching capacity than that of each selector switch.

FIG. 3 shows in more detail the construction of an individual pushbutton assembly. Extending from each push button itself is an actuatinglever 6, one end of which is provided with a slot 7 for receiving aspring 8 and an associated backing plate 9. An upturned tag 10 formed oneach lever is arranged to engage a corresponding cam surface 11 formedon the latch bar 3 as indicated in detail in FIGS. 4 (a), (b), (c), (d)and (e). Each lever supports a contact carrier 12 as shown in FIGS. 5and 6, a T-shaped cut-out 13 in the lever being arranged to receive acomplementary projection (see FIG. 6) formed on the underside of thecarrier. The contact carrier is shown in plan view in FIG. 5 and has,for example, six contact clips 15 which are arranged to engage theterminals 16 of a corresponding stator 17 carried by a bracket 18secured to the base plate 1. FIG. 6 illustrates how each stator isassembled to its corresponding contact carrier and shows the clips 15 inthe not-operated" position.

In the fully retracted position of the actuating lever, the tag and thecam surface on the latch are in the positions shown in FIG. 4(a) and thecontact deployment as in FIG. 7(a).

Initial depression of the push button as shown in FIG. 4(b) is notsufficient significantly to disturb the push button switch contactswhich remain of but is sufficient to cause the tag 10 to move along thecam surface 11 resulting in movement to the right of the latch bar andbreaking of the microswitch contacts. Further depression of the pushbutton causes further movement of the latch bar (see FIG. 4(c)),maintaining the microswitch operated and off" and breaking the pushbutton switch contacts as shown in FIG. 7(e). Continued depression ofthe push button causes continued movement of the latch bar (FIG. 411)which causes the microswitch to remain in the operated condition and thepush button switch contacts to make as shown in FIG. 7(d). Depression ofthe push button beyond the position shown in FIG. 4(d) causes the latchbar to be returned to the left by the spring biased microswitch plungeruntil the tag positively engages the latch as shown in FIG. 4(e) so thatthe microswitch contacts remake as shown in FIG. 7(e).

For convenience, FIGS. 7(a) to (e) illustrate single pole switches 2.Such switches are not excluded from the ambit of the invention, but itwill be appreciated from FIGS. 1, 5 and 6 that in the particular examplepresently being described these switches are of the multi-pole typehaving, for example, a six-pole changeover configuration so that complexswitching off and between several loads is possible. Again, in FIGS.7(a) to (e), the safety switch 4 is connected between the supply and theselector switches 2. However, it will be understood that the switch 4may be connected anywhere in the supply circuit for the load to becontrolled, for example, between the switches 2 and the load or betweenthe supply and the load.

It will be appreciated from the foregoing description that while aparticular push button switch is moved from of to on, current supply toit is cut off by virtue of the microswitch being opened. However, themechanical relationship between the actuating levers, latch bar andmicroswitch plunger is such that movement of the switch button iscompletely interdependent whereby if one switch is in its on position,it can be returned to its off position by moving another switch from offto on". Consequently, current supply to the switches will be cut off bythe microswitch not only while a push button switch is moved from off"to on but also when retracted from on to off.

As an alternative to the push button switch assembly described above, arotary switch could be employed. The rotary switch would be of the pushin order to turn" type, the pushing action serving to actuate the safetyor microswitch. The sequence would then be push" thereby cutting off thesupply by opening the safety switch, turn to select or change aparticular program and then release to reestablish the supply by closingthe safety switch.

The main feature of the switch assemblies described above is that whilea particular selector switch is in the process of switching, it isisolated from the supply by the safety switch. Consequently, if theassembly is required to switch high current loads, each selector switchcan have a comparatively low switching capacity it only being necessaryto provide the microswitch with a relatively high switching capacity tomeet the switching load requirements. Consequently, the switchassemblies described have application wherever switching off high powerloads is required, for example, in the control of central heatingsystems.

I claim:

1. An electrical switch means comprising in combination a plurality ofselector switches each having operative and inoperative conditions, asafety switch, mechanical actuating means movable to operate saidselector switches and operatively connected to said safety switch, andelectrical connections interconnecting said safety switch with each saidselector switch, said safety switch controlling current supply to saidselector switches and having a first position in which current can besupplied to said selector switches and a second position in whichcurrent cannot be so supplied, said actuating means having first,second, third, and fourth positions and being movable consecutively fromsaid first position in which each of said selector switches is in one ofits conditions and said safety switch is in its said first position, tosaid second position in which each of said selector switches is, and hasremained, in said one condition and said safety switch is in its saidsecond position, to said third position in which at least one saidselector switch is in its said other condition and said safety switchis, and has remained, in its said second position, and into said fourthposition in which the said at least one selector switch is, and hasremained, in its said other condition and said safety switch is in itssaid first position, said safety switch having a current switchingcapacity higher than that of each said selector switch and sufficient tomeet predetermined switching load requirements.

2. An electrical switch means as claimed in claim 1, in which saidactuating means comprises a longitudinally movable latch bar operativelyconnected to said safety switch and a plurality of spring-loaded pushbuttons each for actuating a respective one of said selector switches,each said push button having a longitudinally movable lever connected tosaid latch bar to effect longitudinal movement thereof.

3. An electrical switch means as claimed in claim 2, in which said latchbar is provided with a plurality of cam surfaces and each said lever isprovided with an abutment member, each of said abutment members beingengageable with a corresponding one of said surfaces to effectlongitudinal movement of said latch bar.

4. An electrical switch means as claimed in claim 3, in which each ofsaid cam surfaces is provided with an undercut portion so that after apredetermined movement of said latch bar in one direction, said abutmentmember disengages said cam surface and latches in said undercut portion.

5. An electrical switch means as claimed in claim 4, in which said latchbar is spring biased in a direction opposite to said one direction sothat when at least one of said abutment members leaves its correspondingcam surface, said latch bar is moved in said opposite direction and atleast one of said abutment members latches in said undercut portion.

6. An electrical switch as claimed in claim 2, in which each of saidselector switches comprises two sets of electrical contacts, one setbeing supported on a corresponding one of said levers and said other setbeing mounted on a stationary support.

7. An electrical switch as claimed in claim 2, in which movement of eachof said levers is at right-angles to said movement of said latch bar.

8. An electrical switch as claimed in claim 2, in which said safetyswitch is of the snap-action type and is provided with a spring biasedplunger against which one end of said latch bar engages.

1. An electrical switch means comprising in combination a plurality ofselector switches each having operative and inoperative conditions, asafety switch, mechanical actuating means movable to operate saidselector switches and operatively connected to said safety switch, andelectrical connections interconnecting said safety switch with each saidselector switch, said safety switch controlling current supply to saidselector switches and having a first position in which current can besupplied to said selector switches and a second position in whichcurrent cannot be so supplied, said actuating means having first,second, third, and fourth positions and being movable consecutively fromsaid first position in which each of said selector switches is in one ofits conditions and said safety switch is in its said first position, tosaid second position in which each of said selector switches is, and hasremained, in said one condition and said safety switch is in its saidsecond position, to said third position in which at least one saidselector switch is in its said other condition and said safety switchis, and has remained, in its said second position, and into said fourthposition in which the said at least one selector switch is, and hasremained, in its said other condition and said safety switch is in itssaid first position, said safety switch having a current switchingcapacity higher than that of each said selector switch and sufficient tomeet predetermined switching load requirements.
 2. An electrical switchmeans as claimed in claim 1, in which said actuating means comprises alongitudinally movable latch bar operatively connected to said safetyswitch and a plurality of spring-loaded push buttons each for actuatinga respective one of said selector switches, each said push button havinga longitudinally movable lever connected to said latch bar to effectlongitudinal movement thereof.
 3. An electrical switch means as claimedin claim 2, in which said latch bar is provided with a plurality of camsurfaces and each said lever is provided with an abutment member, eachof said abutment members being engageable with a corresponding one ofsaid surfaces to effect longitudinal movement of said latch bar.
 4. Anelectrical switch means as claimed in claim 3, in which each of said camsurfaces is providEd with an undercut portion so that after apredetermined movement of said latch bar in one direction, said abutmentmember disengages said cam surface and latches in said undercut portion.5. An electrical switch means as claimed in claim 4, in which said latchbar is spring biased in a direction opposite to said one direction sothat when at least one of said abutment members leaves its correspondingcam surface, said latch bar is moved in said opposite direction and atleast one of said abutment members latches in said undercut portion. 6.An electrical switch as claimed in claim 2, in which each of saidselector switches comprises two sets of electrical contacts, one setbeing supported on a corresponding one of said levers and said other setbeing mounted on a stationary support.
 7. An electrical switch asclaimed in claim 2, in which movement of each of said levers is atright-angles to said movement of said latch bar.
 8. An electrical switchas claimed in claim 2, in which said safety switch is of the snap-actiontype and is provided with a spring biased plunger against which one endof said latch bar engages.